The present invention relates to vacuum pumps and in particular, xe2x80x9chybridxe2x80x9d or compound vacuum pumps which have two or more sections with different operational modes for improving the operating range of pressures and throughput of the pumps.
In European patent application number 97302890 (EP 0 805 275 A2), there is described a compound vacuum pump having a regenerative section and a Holweck section.
A disadvantage of vacuum pumps, which consist of or include a regenerative section, is that the regenerative section is sensitive to dust and other foreign bodies. Dust and other foreign bodies have been known to cause blade breakage and erosion or occlusion within the fine running tolerances associated with regenerative sections.
It is an object of the present invention to provide a compound vacuum pump having Holweck and regenerative sections, and including a trap for preventing or inhibiting dust and other foreign bodies from reaching the inlet of the regenerative section.
According to the present invention, there is provided a compound vacuum pump consisting of a Holweck section upstream of a regenerative section, and means associated with the Holweck section for separating and trapping dust and other foreign bodies within the Holweck section.
In one embodiment, the Holweck section includes alternate stationary and rotating cylinders, the stationary cylinders being mounted on a stator and the rotating cylinders being mounted for rotary movement with a rotor; and separating and trapping means including an annular abutment formed on the radially innermost rotating cylinder.
In a further embodiment, the Holweck section includes alternate stationary and rotating cylinders, the stationary cylinders being mounted on a stator and the rotating cylinders being mounted for rotary movement with a rotor; and separating and trapping means being located between the last stage of the Holweck section and the inlet stage of the regenerative section, the separating and trapping means including a cavity formed in the Holweck stator and immediately opposite said cavity a blade fixed for rotary movement extending radially outwardly from the outermost rotating cylinder.